EP2772889B1

EP2772889B1 - Apparatus and method of using a light conduit in a position detector

Info

Publication number: EP2772889B1
Application number: EP14154570.7A
Authority: EP
Inventors: Tianfeng Zhao; Zhongya Jiang; Paul M. Popowski; Guenter Watzlawik
Original assignee: Honeywell International Inc
Current assignee: Honeywell International Inc
Priority date: 2013-02-27
Filing date: 2014-02-10
Publication date: 2018-05-16
Anticipated expiration: 2034-02-10
Also published as: ES2674937T3; CA2842633A1; CN104008620B; EP2772889A1; US8982360B2; CN104008620A; US20140240717A1

Description

FIELD

The application pertains to position detectors, such as door or window intrusion sensors. More particularly, the application pertains to such detectors which incorporate a fiber optic element, or other type of light pipe, to return light transmitted from a detector mounted on a movable door or window through a portion of an adjacent non-movable frame to the detector for analysis.

BACKGROUND

There are two kinds of technology that are widely used in implementing door/window intrusion sensors. One includes a combination of a reed switch with a magnet (mechanical contacts). The other includes a source, an infrared (IR) sensor and a reflector. Unfortunately, each of these methods could be defeated by a person having limited knowledge of the sensors.
Mechanical contacts can be easily defeated from the outside by using an additional magnet to keep the reed switch actuated while the window or door is being opened.
Known intrusion sensors based on IR transmission have constantly transmitted the IR. Such devices may be defeated by shining a light, such as flashlight, at the IR sensor, or using a thin mirror as a reflector to defeat the device. GB 2 013 332 A discloses a position detector comprising: an optical source; an optical sensor; control circuits coupled to the source and the sensor wherein the circuits intermittently energize the source with a predetermined signal; and a radiant energy conduit with an input end and an output end, wherein the input end is coupled to the source when the conduit is in a first position relative to the source, and the output end is coupled to the sensor, and wherein if the conduit moves from the first position, the coupling is disrupted.

SUMMARY OF THE INVENTION

The present invention provides a detector as defined in claim 1. The detector may include the features of any one or more of dependent claims 2 to 10.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 illustrates a block diagram of a detector in accordance herewith;
Fig. 2 is a flow diagram of an exemplary method of operating a detector as in Fig. 1;
Fig. 3 illustrates a timing diagram of a transmitted and a received signal of an embodiment hereof;
Fig. 4 illustrates a variation of the detector of Fig. 1; and
Fig. 5 is a timing diagram of a coded transmitted and received signal.

DETAILED DESCRIPTION

While disclosed embodiments can take many different forms, specific embodiments thereof are shown in the drawings and will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles thereof as well as the best mode of practicing same, and is not intended to limit the application or claims to the specific embodiment illustrated.
In one aspect, embodiments hereof include a door, or window detector, mountable on one of a frame, or a door or a window, transmits a coded beam of radiant energy, for example, infrared light toward a second element, such as a door or window or a frame. A fiber optic member can be installed in the second element, such as the adjacent door or window, or frame.
The beam of radiant energy can be transmitted from a source, via the fiber optic member, back to a sensor. The detector and the fiber optic member are in alignment only when the door, or window, is in a predetermined position relative to the adjacent member, such as the respective frame.
For example, if the position to be monitored corresponds to a closed door or window, the detector will receive the returned, coded, beam of radiant energy transmitted via the fiber optic member only when the door or window is closed. If the door or window is moved relative to the frame, the transmission through the fiber optic member will be disrupted and the detector will immediately be able to detect the movement and transmit an alarm indictor to an associated security monitoring system.
According to the invention, the fiber optic member is tapered and has a variable, decreasing radius from input end to output end. A security code can be used to pulse modulate the transmitted light. Alternately, the transmitted light can be modulated by phase shifting, frequency modulation, pulse duration modulation, or the like to increase the security of the transmitted signal. An attacker would have great difficulty, and probably not be able to replicate the transmitted, modulated sequence.
With respect to the figures, Fig. 1 illustrates a detector 10 according to an example. Examples hereof advantageously use a light transmitting conduit, such as member 12, to securely transmit a beam of radiant energy, for example infrared light. The arrows in conduit 12 in Fig. 1 represent the direction of transmission of radiant energy as further discussed below.
Detector 10 includes a housing 16 which can be attached to a door frame, a window frame, a door or a window without limitation. Housing 16 carries control circuits 18 which could be implemented, at least in part by a programmable processor 18-1 and executable instructions, software, 18-2. The control circuits 18 include an input/output interface 18-3 which can be in wired or wireless communication via a medium W displaced monitoring system M. A plurality of detectors, 10-1... 10-n, corresponding to detector 10 can be in communication with system M.
As discussed above, control circuits 18 can activate drive circuits 20a, via a modulated signal, for example a pulse sequence, to energize emitter, source 20b. Emitter 20b in turn outputs a modulated beam of radiant energy, such as infrared, which is coupled to conduit or light pipe 12 when the housing 16 exhibits a predetermined relationship with the conduit or light pipe 12. For example, when the door is closed against the frame or the window is closed against the frame.
In the above condition, the light beam travels through the conduit 12 and is then coupled to detector 22a, processed by receiving circuits 22b, and then made available to control circuits 18. If the transmission path of the beam is disrupted, by opening the door or window; for example, the control circuits can respond to the loss of radiant energy by forwarding an alarm indicator to the system M.
Those of skill will understand that a variety of processes to modulate the radiant energy beam output by source, or emitter, 20b can be used.
Examples as in Fig. 1 provide a low cost solution to door/window position sensing using a radiant energy conductor 12, such as a light pipe or fiber optic member for transmission. The fiber optic member 12 provides a high efficiency transmission medium which promotes detection of received radiant energy.
Further, by using the control circuits 18 to generate and transmit an encrypted data packet such as by randomly varying the pattern of light or by using various types of frequency modulation, the detector 10 can be expected to be more reliable and more difficult to be defeated. Since examples hereof exhibit both low cost and low power consumption, they can be powered by a battery 26 and are suitable for wireless door/window applications.
Fig. 2 illustrates an exemplary method 200 of operating a detector as in Fig. 1. Process 200 is exemplary and is not a limitation hereof. Other processes can be used. Fig. 3 illustrates a timing diagram of transmitted radiant energy pulses and received radiant energy pulses in accordance with the method of Fig. 2.
With respect to Figs. 2, 3 the detector 10 is initialized, as at 210. As at 220, a pulse is emitted by source 20b and received at sensor 22a. If the received optical signal exceeds a predetermined threshold, such as threshold 1, as at 230, the next portion of the received pulse sequence is evaluated, as at 240. If the received value is below a predetermined threshold, such as threshold 2, as at 250 the process 200 is repeated since the respective door and frame, or window and frame are exhibiting the predetermined, closed state. Otherwise, an alarm can be output, as at 260.
Fig. 4 illustrates a variable diameter, tapered fiber optic member 12-1 usable with the detector of Fig. 1, according to the invention.
Fig. 5 illustrates an exemplary timing diagram of coded output control pulses, illustrated at C1, which can be produced by control circuits 18 and which generate coded radiant energy pulses at emitter 20b. The output pulses from emitter 20b are transmitted, via the fiber optic member 12 to the sensor 22a. Coded, radiant energy signals, illustrated at C2, received by sensor 22a can be converted to electrical waveforms and analyzed in the circuitry 18 of the detector 10 of Fig. 1.
It will be understood that the control circuits, and instructions 18-2 can present a time varying modulated sequence of optical signals, to be transmitted by conduit 12 and subsequently received at sensor 22a and analyzed by the control circuits 18. Such time varying modulated signal packets can be expected to provide enhanced security for the detector 10 as well as the other members of the plurality 10-i.
From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the scope hereof. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims. Further, logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Other steps may be provided, or steps may be eliminated, from the described flows, and other components may be add to, or removed from the described embodiments.

Claims

A position detector (10) comprising:
an optical source (20b);

an optical sensor (22a);

control circuits (18) coupled to the source (20b) and the sensor (22a) wherein the circuits (18) intermittently energize the source (20b) with a predetermined signal; and

a radiant energy conduit (12) with an input end and an output end and a variable diameter that decreases from the input end to the output end, the input end is coupled to the source (20b) when the conduit (12) is in a first position relative to the source (20b), and the output end is coupled to the sensor (22a), and wherein if the conduit moves from the first position, the coupling is disrupted.
A detector (10) as in claim 1 wherein the control circuits (18) include drive circuits (20a), coupled to the source (20b) and where the drive circuits (20a) energize the source (20b) intermittently.
A detector (10) as in claim 1 which includes a housing (16) which carries the source (20b), the sensor (22a) and the control circuits (18).
A detector (10) as in claim 3 wherein the conduit (12) is displaced from and outside of the housing (16).
A detector (10) as in claims 4 wherein the control circuits (18) modulate the source (20b) to generate a beam of radiant energy wherein modulation comprises at least one of pulse position modulation, pulse duration modulation, frequency modulation and phase modulation.
A detector (10) as in claim 5 which include interface circuits (18-3) coupled to the control circuits (18) that communicate via a medium (M) with displaced supervisory circuitry.
A detector (10) as in claim 6 wherein the interface circuits (18-3) communicate wirelessly with the displaced supervisory circuitry and wherein the housing (16) carries a battery (26) coupled at least to the control circuits (18).
A detector (10) as in claim 6 wherein the conduit (12) comprises a fiber optic member.
A detector (10) as in claim 1 wherein the predetermined signal is a coded signal.
A detector (10) as in claim 9 wherein the control circuits (18) modulate the source (20b) to generate a beam of radiant energy wherein modulation comprises at least one of pulse position modulation, pulse duration modulation, frequency modulation and phase modulation.